by the way, you should find a reasonable excuse rather than the issue you mentioned

其实，美国的风俗是伴娘自己买礼服的。新娘会送伴娘礼物表示感谢。
她不出礼服钱并不是她的错，但是不理解你的难处，在你选礼服上面为难你就不大好了。
其实能够给人做伴娘伴郎的都要是很好的朋友，不计较钱的那种。如果觉得交情没到那个程度就算了。
要拒绝的话，早拒绝，不要等到婚礼筹划得差不多了再和人家说。这样人家也好找别人。

Nod, tradition应该是伴娘自己买礼服的

Agree with last two posts- the bridesmaids usually have to buy their own dress.  It sounds like she is not paculiar about the style of the dress if you are shopping on your own.  So why not go to a cheaper store and get something you can wear that once.  Usually anything that is associated with weddings doubles or triples in price.  It should be fairly easy to find something at a reasonable price in a department store like Macy's.  Since you are the only bridesmaid, you don't have to match colors with anyone, so that should make it easier on you as well.  My thought on this is that if you really don't want to do it, tell her now so that she can find alternatives as wedding planning is stressful enough.  If you want to do it but don't want to get the dresses you were quoting, then find a cheaper dress if you are just going to wear it once.

thanks a lot, i will refuse her, since she is not even my friend, i really don't want to do this for her